Kling 4.0

Kling 4.0 uses capability-specific creation paths. The model name is part of each path; do not send model or model_name in the request body. Configure output with settings and general options with options.

Create task

POST /kling/v2/text-to-video/kling-4.0

cURL

curl --request POST \
  --url 'https://www.anyfast.ai/kling/v2/text-to-video/kling-4.0' \
  --header 'Authorization: Bearer YOUR_ANYFAST_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
    "prompt": "A red car drives slowly along a rain-soaked street as the camera pans right. Realistic style, natural rain sound, no subtitles, and no sudden cuts.",
    "settings": {
      "resolution": "720p",
      "aspect_ratio": "21:9",
      "duration": 3
    },
    "options": {
      "watermark_info": {
        "enabled": false
      }
    }
  }'

Request headers

string

required

Bearer authentication. Use Bearer YOUR_ANYFAST_API_KEY.

string

default:"application/json"

required

Request body format.

Request body

string

required

Video description. You can include both desired and unwanted content. Prompt limits depend on character type; see the prompt length section.

object

Output resolution, duration, and aspect ratio.

string

720p or 1080p. Explicitly setting a value is recommended.

integer

Integer from 3 to 30 seconds. Explicitly setting a value is recommended. If omitted, the prompt duration is used when clear; otherwise the default is 10 seconds.

string

21:9, 16:9, 9:16, or 1:1. adaptive is also supported by the shared output settings.

object

General task options.

boolean

default:false

Whether to additionally generate a watermarked version.

string

Caller-defined task identifier. Keep it unique within the current user scope. It does not replace the system task ID or guarantee duplicate-charge prevention.

string

Task-status callback URL defined by the official protocol. Confirm support on the current channel before use.

Create response

200

{
  "code": 0,
  "message": "",
  "request_id": "REQUEST_ID",
  "data": {
    "id": "asyntask_EXAMPLE",
    "status": "submitted",
    "create_time": 1793672435967,
    "update_time": 1793672435967,
    "external_id": ""
  }
}

integer

Business status code; the success example is 0.

string

API message.

string

Request tracing identifier, when returned.

string

System task ID. Save it for querying.

string

Current task status.

integer

Creation time as a Unix timestamp in milliseconds.

integer

Update time as a Unix timestamp in milliseconds.

string

Caller-defined task ID; may be empty if unset.

Create task

POST /kling/v2/image-to-video/kling-4.0

cURL

curl --request POST \
  --url 'https://www.anyfast.ai/kling/v2/image-to-video/kling-4.0' \
  --header 'Authorization: Bearer YOUR_ANYFAST_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
    "contents": [
      {
        "type": "prompt",
        "text": "Start from @start and preserve the person's identity and composition. The person smiles and raises a hand as a breeze moves their hair. Add natural wind sound. Use one continuous shot, no subtitles."
      },
      {
        "type": "first_frame",
        "url": "https://example.com/first-frame.jpg",
        "id": "start"
      }
    ],
    "settings": {
      "resolution": "720p",
      "duration": 3
    },
    "options": {
      "watermark_info": {
        "enabled": false
      }
    }
  }'

Request headers

string

required

Bearer authentication. Use Bearer YOUR_ANYFAST_API_KEY.

string

default:"application/json"

required

Request body format.

Request body

object[]

required

Prompt and keyframe images. Include a prompt item. Image input supports up to 10 images.

string

required

Use prompt, first_frame, middle_frame, or last_frame for this workflow.

string

Prompt text when type is prompt. Use an asset ID as @id to reference an image in the prompt.

string

Publicly accessible image URL, or a supported Base64 image value.

string

Optional unique asset ID used by the prompt. IDs must not repeat within a task.

object

Output settings.

string

720p or 1080p.

integer

Integer from 3 to 30 seconds.

string

Optional output ratio. For keyframe input, use images with the intended composition; the example omits this field.

boolean

default:false

Whether to additionally generate a watermarked version.

string

Optional caller-defined task ID. It does not replace the system task ID or guarantee duplicate-charge prevention.

string

Optional callback URL; confirm current-channel support before use.

Create response

200

{
  "code": 0,
  "message": "",
  "request_id": "REQUEST_ID",
  "data": {
    "id": "asyntask_EXAMPLE",
    "status": "submitted",
    "create_time": 1793672435967,
    "update_time": 1793672435967,
    "external_id": ""
  }
}

string

System task ID. Save it for querying.

string

Initial task status, such as submitted.

integer

Creation Unix timestamp in milliseconds.

integer

Update Unix timestamp in milliseconds.

Keyframe types

Type	Use	Fields
`prompt`	Describe action, camera, and sound	`text`
`first_frame`	First-frame image	`url`, optional `id`
`middle_frame`	Intermediate keyframe	`url`, optional `id`
`last_frame`	Last-frame image	`url`, optional `id`

Assign unique IDs when the prompt needs to reference keyframes. Up to 10 images are supported. Image requirements are listed in the Input requirements tab.

Create task

POST /kling/v2/omni-video/kling-4.0

cURL

curl --request POST \
  --url 'https://www.anyfast.ai/kling/v2/omni-video/kling-4.0' \
  --header 'Authorization: Bearer YOUR_ANYFAST_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
    "contents": [
      {
        "type": "prompt",
        "text": "Preserve the face, hairstyle, and clothes of the person in @actor. Use the action pacing from @motion. Show the person moving naturally in a bright training studio. Keep the camera steady and add no subtitles."
      },
      {
        "type": "refer_image",
        "url": "https://example.com/character.jpg",
        "id": "actor"
      },
      {
        "type": "feature_video",
        "url": "https://example.com/motion.mp4",
        "id": "motion"
      }
    ],
    "settings": {
      "resolution": "720p",
      "aspect_ratio": "1:1",
      "duration": 3
    },
    "options": {
      "watermark_info": {
        "enabled": false
      }
    }
  }'

Request headers

string

required

Bearer authentication. Use Bearer YOUR_ANYFAST_API_KEY.

string

default:"application/json"

required

Request body format.

Request body

object[]

required

Prompt and reference assets. Include a prompt item. Asset IDs must be unique within a task.

string

required

Use prompt, refer_image, first_frame, middle_frame, last_frame, feature_video, or base_video.

string

Prompt text for a prompt item. Use @id to specify how a reference asset should be used.

string

Publicly accessible URL for an image or video asset. Images may also use supported Base64 content.

string

Unique asset ID used to reference an item from the prompt.

object

Output settings.

string

720p or 1080p.

integer

Integer from 3 to 30 seconds. If omitted, use prompt duration, then base_video duration, then default to 10 seconds.

string

21:9, 16:9, 9:16, 1:1, or adaptive.

boolean

default:false

Whether to additionally generate a watermarked version.

string

Optional caller-defined task ID. It does not replace the system task ID or guarantee duplicate-charge prevention.

string

Optional callback URL; confirm current-channel support before use.

Create response

200

{
  "code": 0,
  "message": "",
  "request_id": "REQUEST_ID",
  "data": {
    "id": "asyntask_EXAMPLE",
    "status": "submitted",
    "create_time": 1793672435967,
    "update_time": 1793672435967,
    "external_id": ""
  }
}

string

System task ID. Save it for querying.

string

Initial task status, such as submitted.

integer

Creation Unix timestamp in milliseconds.

integer

Update Unix timestamp in milliseconds.

Reference content types

Type	Use	Main fields
`prompt`	Describe generation or editing requirements	`text`
`refer_image`	Appearance, scene, or style reference	`url`, `id`
`first_frame`	First-frame constraint	`url`, `id`
`middle_frame`	Intermediate keyframe constraint	`url`, `id`
`last_frame`	Last-frame constraint	`url`, `id`
`feature_video`	Motion or other feature reference	`url`, `id`
`base_video`	Source video for editing	`url`, `id`

The protocol also defines element and voice assets for previously created characters and voices. These require corresponding assets and management capabilities; this reference does not describe those management APIs.

Duration selection

Duration is determined in this order: explicit settings.duration, clear duration intent in the prompt, base_video duration, then the 10-second default. Submit at most one base_video.

Create task

POST /kling/v2/omni-video/kling-4.0Submit the source clip as base_video. Describe both the change and the content that should remain unchanged.

cURL

curl --request POST \
  --url 'https://www.anyfast.ai/kling/v2/omni-video/kling-4.0' \
  --header 'Authorization: Bearer YOUR_ANYFAST_API_KEY' \
  --header 'Content-Type: application/json' \
  --data '{
    "contents": [
      {
        "type": "prompt",
        "text": "Edit @base: change only the red ceramic cup in the person's hand to blue. Preserve the person's face, clothes, hand movement, background, camera motion, dialogue, and ambient sound. Do not add objects or subtitles."
      },
      {
        "type": "base_video",
        "url": "https://example.com/source-video.mp4",
        "id": "base"
      }
    ],
    "settings": {
      "resolution": "720p",
      "aspect_ratio": "adaptive"
    },
    "options": {
      "watermark_info": {
        "enabled": false
      }
    }
  }'

Request headers

string

required

Bearer authentication. Use Bearer YOUR_ANYFAST_API_KEY.

string

default:"application/json"

required

Request body format.

Request body

object[]

required

Prompt and source video. Include a prompt item and at most one base_video item.

string

required

Use prompt and base_video for this editing example. Other Omni reference asset types are listed in the Omni reference tab.

string

required

Describe what to change and what to preserve. Use @id to refer to the source video.

string

required

Publicly accessible source-video URL.

string

required

Unique asset ID referenced by the prompt.

string

720p or 1080p.

string

Set adaptive to determine the ratio from the prompt or input video.

integer

Optional integer from 3 to 30 seconds. If omitted, duration follows explicit prompt intent, then the source video, then defaults to 10 seconds.

boolean

default:false

Whether to additionally generate a watermarked version.

string

Optional caller-defined task ID. It does not replace the system task ID or guarantee duplicate-charge prevention.

string

Optional callback URL; confirm current-channel support before use.

Create response

200

{
  "code": 0,
  "message": "",
  "request_id": "REQUEST_ID",
  "data": {
    "id": "asyntask_EXAMPLE",
    "status": "submitted",
    "create_time": 1793672435967,
    "update_time": 1793672435967,
    "external_id": ""
  }
}

string

System task ID. Save it for querying.

string

Initial task status.

integer

Creation Unix timestamp in milliseconds.

integer

Update Unix timestamp in milliseconds.

Set settings.duration when you need to control the output length. The example omits it so the source video duration is used when no explicit duration intent is present in the prompt.

Query tasks

GET /kling/v2/tasks?task_ids=YOUR_TASK_IDUse the system task ID from the create response’s data.id. Query with the same AnyFast API key used to create the task. The query path does not require a model name or upstream task ID.

cURL

curl --request GET \
  --url 'https://www.anyfast.ai/kling/v2/tasks?task_ids=YOUR_TASK_ID' \
  --header 'Authorization: Bearer YOUR_ANYFAST_API_KEY'

Query response

200

{
  "code": 0,
  "message": "",
  "data": [
    {
      "id": "asyntask_EXAMPLE",
      "status": "succeeded",
      "create_time": 1793672435967,
      "update_time": 1793672563000,
      "outputs": [
        {
          "type": "video",
          "url": "https://example.com/generated-video.mp4",
          "duration": "3.042"
        }
      ]
    }
  ]
}

Response fields

integer

Business status code; the success example is 0.

string

API message.

object[]

Task records matching the supplied task IDs. The query response uses an array; the create response uses an object.

string

System task ID.

string

submitted, processing, succeeded, or failed.

integer

Creation Unix timestamp in milliseconds.

integer

Last-update Unix timestamp in milliseconds.

object[]

Generated outputs, available when the task succeeds.

string

Output type. Select video for the generated video.

string

Video result URL.

string

Actual duration in seconds; may be a decimal string.

string

Watermarked result URL, present only when provided.

Query every 10–20 seconds and set an application-level wait limit. If the limit is reached, keep the task ID and query it later; do not immediately resubmit the same generation request. Download result URLs soon after generation because they may expire or include access signatures.

Image requirements

Property	Requirement
Formats	JPG, JPEG, PNG
Maximum size	30 MB per image
Dimensions	At least 300 px wide and 300 px high
Aspect ratio	2:5–5:2
Count	Up to 10 images

Images can be submitted by URL or supported Base64 content. URLs must be directly accessible to the service and return the image file.

Video requirements

Property	Requirement
Formats	MP4, MOV
Maximum size	300 MB per video
Duration	Each video and total input-video duration must be 3–30 seconds
Dimensions	700–4553 px wide and high; up to 8,294,400 total pixels
Aspect ratio	2:5–5:2
Input frame rate	24–60 fps
Output frame rate	24 fps

Videos use URLs. The service must be able to access each URL directly and retrieve the video file.

Omni reference limits

Images, videos, elements, and voices combined: up to 15 assets.
With no video-character elements, up to 5 reference videos.
With video-character elements, the combined number of video-character elements and reference videos must not exceed 5.
Total input-video duration includes feature reference videos, the video being edited, and video-character elements.
Submit at most one base_video per task.

Prompt length

The limits apply to a text-to-video prompt or the prompt item’s text in contents:

Text	Limit
English only	26,000 characters
Non-English only	11,000 characters
Mixed text	English characters ÷ 26,000 + non-English characters ÷ 11,000 ≤ 1

Creation is asynchronous. A successful create response means the task was accepted; query the returned data.id to retrieve its status and result.

Overview

Native Compatible Endpoints

Model APIs

Create task

Request headers

Request body

Create response

Create task

Request headers

Request body

Create response

Keyframe types

Create task

Request headers

Request body

Create response

Reference content types

Duration selection

Create task

Request headers

Request body

Create response

Query tasks

Query response

Response fields

Image requirements

Video requirements

Omni reference limits

Prompt length

​Create task

​Request headers

​Request body

​Create response

​Create task

​Request headers

​Request body

​Create response

​Keyframe types

​Create task

​Request headers

​Request body

​Create response

​Reference content types

​Duration selection

​Create task

​Request headers

​Request body

​Create response

​Query tasks

​Query response

​Response fields

​Image requirements

​Video requirements

​Omni reference limits

​Prompt length

Create task

Request headers

Request body

Create response

Create task

Request headers

Request body

Create response

Keyframe types

Create task

Request headers

Request body

Create response

Reference content types

Duration selection

Create task

Request headers

Request body

Create response

Query tasks

Query response

Response fields

Image requirements

Video requirements

Omni reference limits

Prompt length